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Inocybe unicolor

[Basidiomycota > Agaricales > Inocybaceae > Inocybe . . . ]

by Michael Kuo

This interesting fungus appears to be widespread in North America, to judge from collection records in major herbaria--although its wide distribution may also signal the possibility that there are several "cryptic species" involved. It has gone under the name of "Inocybe caesariata" for almost 100 years, but Inocybe expert Brandon Matheny (Matheny & Horman, 2013) tells us that Inocybe caesariata is a poorly known, strictly European species, and that North American mycologist Charles Peck gave the name Inocybe unicolor to our continent's similar species in 1898.

Inocybe unicolor is not really very Inocybe-ish; it almost seems more like a terrestrial species of Pholiota. It is a small to medium-ish mushroom that features a scaly stem and a slightly fibrillose cap that usually becomes scaly as it matures. The gills are pale, dull yellow before they turn brown with maturity, whereupon the densely packed cheilocystidia cause the pale edges to contrast with the faces. The flesh in the very base of the stem is often bright to dull yellow, and mature specimens often have a slightly foul odor. Under the microscope, Inocybe unicolor has smooth, bean-shaped spores and distinctive, long cheilocystidia.

Description:

Ecology: Mycorrhizal; growing alone, scattered, or gregariously under oaks and other hardwoods; late spring through fall; apparently widely distributed in North America, but a bit more common east of the Rocky Mountains. The illustrated and described collections are from Illinois and Indiana.

Cap: 2-5.5 cm; at first convex with an inrolled margin, expanding to planoconvex, broadly bell-shaped, or nearly flat; dry; bald, or fibrillose, becoming finely scaly with brown to orangish brown scales over a pale tan or yellowish ground.

Gills: Broadly attached to the stem or beginning to run down it; close; short-gills frequent; pale yellow at first, becoming brownish yellow and eventually dull brown; edges by maturity pale yellowish to whitish, contrasting with the faces; at first covered with a yellowish cortina.

Stem: 2.5-6 cm long; 3-10 mm thick; more or less equal above a slightly tapered base; dry; creamy and bald near the apex; shaggy with vague bands of brown fibers and scales overall; surface pale brownish; occasionally with a ring zone; basal mycelium whitish above ground, sulphur yellow below.

Flesh: Whitish to yellowish or brownish; often bright to dull yellow in stem base; unchanging when sliced.

Odor: Usually somewhat foul and reminiscent of coal tar, but often not distinctive.

Chemical Reactions: KOH negative, gray, or reddish black on cap surface.

Spore Print: Dull brown.

Microscopic Features: Spores 8-11 x 5-6 µ; ellipsoid or bean-shaped; smooth; walls 0.5-1 µ thick; yellowish to brownish golden in KOH; walls brownish in Melzer's reagent. Pleurocystidia not found. Cheilocystidia abundant; 35-75 x 2.5-7.5 µ; cylindric and flexuous with rounded, subclavate, subcapitate, capitate or (rarely) subacute apices; occasionally slightly ventricose; often septate and clamped at septa; thin-walled; smooth; hyaline to yellowish in KOH. Basidia 4-sterigmate. Lamellar trama parallel. Pileipellis a collapsing trichoderm; elements brown-walled in KOH, smooth, 6-14 µ wide, clamped.

REFERENCES: Peck, 1898. (Saccardo, 1899; Kauffman, 1924 [caesariata]; Phillips, 1991/2005 [caesariata]; Lincoff, 1992 [caesariata]; Matheny & Horman, 2013.) Herb. Kuo 07140307, 07180705, 06211102, 06231101, 08281401, 06071503, 06181501.


Further Online Information:

"Inocybe caesariata" at Roger's Mushrooms

 

Inocybe unicolor

Inocybe unicolor

Inocybe unicolor

Inocybe unicolor

Inocybe unicolor

Inocybe unicolor

Inocybe unicolor
KOH

Inocybe unicolor
Spore print

Inocybe unicolor
Spores

Inocybe unicolor
Cheilocystidia

Inocybe unicolor
Cheilocystidia

Inocybe unicolor
Pileipellis



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Kuo, M. (2016, July). Inocybe unicolor. Retrieved from the MushroomExpert.Com Web site: http://www.mushroomexpert.com/inocybe_unicolor.html